public class Example4_8 {
   public static void main(String args[]) {
       Circle circle = new Circle();
       circle.setRadius(10);
       Circular circular = new Circular();      
       System.out.println("circle的引用:"+circle);
       System.out.println("圆锥的bottom的引用:"+circular.bottom);
       circular.setHeight(5);
       circular.setBottom(circle);
       System.out.println("circle的引用:"+circle);
       System.out.println("圆锥的bottom的引用:"+circular.bottom);
       System.out.println("圆锥的体积:"+circular.getVolme());
       System.out.println("修改circle的半径,bottom的半径同样变化");
       circle.setRadius(20);
       System.out.println("bottom的半径:"+circular.getBottomRadius());
       System.out.println("重新创建circle,cirlce的引用将发生变化");
       circle = new Circle(); 
       System.out.println("circle的引用:"+circle);
       System.out.println("但是不影响circular的bottom的引用");
       System.out.println("圆锥的bottom的引用:"+circular.bottom);
   }
}
